The invention relates to an infusion needle, more particularly for general infusion therapy, having a needle receiving body having a metal cannula and a cylindrical receiving opening connected thereto for receiving applicators, the metal cannula taking the form of an aspiration needle which is enclosed by a somewhat shorter, closely adjoining plastics cannula which terminates conically and is connected to the receiving opening.
In addition to the oral and rectal administration of medicaments, parenteral administration forms one of the bases of present-day therapy. Even though in modern medicine intravenous infusion therapy and arterial injection techniques have partly displaced injection therapy in its three classical forms--i.e., the subcutaneous, intramuscular and intravenous administration of medicaments--, subcutaneous and intracutaneous administration still form a wide range of infusion therapy, more particularly for the treatment of pain and diabetes. They developed in many small steps and over a prolonged period. Methods for bleeding and the supply of medicaments have been known for many years.
The discovery of the circulation of the blood at the beginning of the 17th century created the anatomical and physiological basis for infusion and transfusion. Even at that time the first infusion experiments began, at first on animals and subsequently on human beings also. At first they were unable to achieve any therapeutic effect or any progress in knowledge. Since the reason for the initial failures was probably mainly septic conditions, the invention of the injection syringe in the 19th century first opened up the way to modern injection and infusion therapy. However, a new chapter in the theory of transfusion began only after the discovery of blood groups at the beginning of the present century. Only then could those decisive foundations and techniques be developed which, encouraged by the two world wars and the development of internal medicine and anaesthesiology, are still for the most part valid at the present day.
Subcutaneous injection still plays an important role in the field of pain therapy, although therapeutic subcutaneous injections are a good deal less frequent than they used to be. This decline is partly due to the fact that resorption times are difficult to determine and depend heavily on the state of the particular patient. On the other hand, nowadays more different agents are injected which are incompatible when applied subcutaneously. Nevertheless, subcutaneous techniques, more particularly subcutaneous infusions are still important, more particularly for children. In the case of subcutaneous infusion it is very important for the infusions to be performed in accordance with the laws of the art, since injection into the skin not only causes severe pain, but may lead to violent inflammations, even including skin necroses. Subcutaneous injection is also known to be followed by oedematous swellings accompanied by varying degrees of inflammation, so that the sense of well-being of the patients is often very adversely affected. However, these complications are usually harmless and disappear in a few days. However, in rare cases they may also lead to skin necrosis and via secondary infection to erysipelas and, if the patient's initial condition is unfavourable, to sopsis. Even today, intracutaneous injection still plays an important role in BCG protective inoculation (Bacille-Calmette-Guerin; protective inoculation against tuberculosis). It is frequently used in curative therapy.
In subcutaneous injection or infusion the medicament must be administered by injection into the subcutaneous fatty tissue, while in intracutaneous injection a deposit of medicament comes to lie directly in the skin (cutis). The majority of subcutaneous injections are administered in the zone of the upper arm, the thigh or the chest. In contrast with other injection methods, in subcutaneous injection technique there is no essential difference between the application of this therapy to men, women, children or sucklings.
Whereas in the case of injection the injection needle is after the depositing of a medicament withdrawn from the subcutaneous or intracutaneous tissue, an infusion needle remains at the place of application for a prolonged period, possibly of up to several days. It can quickly be seen that this is unpleasant for the patient, whose freedom of movement is thereby impeded. Unavoidable movements can cause various degrees of pain.
CH-PS 400 463 discloses a cannula for infusions, more particularly for continuous drip infusions, having a needle receiving body having a metal cannula and a cylindrical receiving opening connected thereto. In that known needle the metal cannula takes the form of an aspiration cannula enclosed by a somewhat shorter, closely adjoining plastics cannula which terminates conically and is connected to the receiving opening. This known infusion needle has a metal cannula which comes to lie at a small angle to the surface of the skin in the subcutaneous or intracutaneous tissue. Even if the known infusion needle can be simply attached to the skin, due to the bend it stands out relatively high and therefore chafes, for example, against the patient's clothing, something which again may cause the patient pain.
It is therefore an object of the invention so to design and further develop the infusion needle described in greater detail hereinbefore that the best possible adaptation to the patient's movements is achieved, without having to abandon the secure retention of the infusion needle at the place of application.